A rotary cone rock bit is that part of a rotary drill string that performs the actual drilling operations. As a drill string rotates, the bit disintegrates the earth formation and forms a bore hole. The bit comprises a body attached to the drill string and journal legs extending downward from the body. The lower end of each journal leg forms a cantilever supporting shaft or bearing pin and rotatably mounted to each bearing pin is a cone cutter specifically designed for the formation to be cut.
Previously, the cone cutter was retained on the bearing pin by cutting semicircular grooves in the inner wall of the cone cutter and the outer wall of the bearing pin. These grooves are assembled to form a toroidal channel, which channel was filled with ball bearings for retention as well as rotational purposes. Though this method is sound for retention purposes, the grooves and ball bearings occupy a large longitudinal space and consequently the bushing area of the bearing pin must be shortened. Such a short bushing destabilizes the cone cutter and increases bushing wear and the tendency of the cone to wobble. Increased wobbling puts strain on the cone seal, which then wears rapidly thereby allowing lubricant to escape and abrasive and destructive material to enter the bearing area. This decreases the durability and longevity of the bit as a whole.
Other retention methods include snap rings, see U.S. Pat. No. 4,491,428 and segmented rings, see U.S. Pat. No. 4,444,518. These retention methods require close tolerances, are difficult to manufacture, and have significant slippage problems.